Cardiac Murmur Introduction Notes

Cardiac Murmur Introduction

A cardiac murmur is an abnormal or unusual heart sound heard by a stethoscope along with normal heart sounds. A cardiac murmur is also called an abnormal heart sound or cardiac bruit. The abnormal sound is produced because of the change in the pattern of blood flow.

• Normally, blood flows in streamline through the heart and the blood vessels.
• However, during the abnormal conditions.’ of valvular diseases, the blood flow becomes turbine. d produces the cardiac murmur.
• The cardiac murmur is heard by placing the- piece of the stethoscope over the auscultatory areas.

Read And Learn More: Medical Physiology Notes

• The murmur due to disease of a particular valve is heard well over the auscultatory area of that valve.
• Sometimes, the murmur is felt by palpation as “thrills”.
• In some patients, the murmur is heard without any aid even at a distance of a few feet away from the patient.
• The murmur is produced because of valvular diseases, septal defects, and vascular defects.

Valvular diseases are of two types:

1. Stenosis
2. Incompetence.

Stenosis

• Stenosis means the narrowing of the heart valve.
• The blood flows rapidly with turbulence through the narrow orifice of the valve resulting in a murmur.

Incompetence

• Incompetence refers to the weakening of the valve in the heart. When the valve becomes weak, it cannot close properly.
• It causes backflow of blood resulting in turbulence. This disease is also called regurgitation or valvular insufficiency.

Classification Of Murmur

Cardiac murmur is classified into three types:

1. Systolic murmur
2. Diastolic murmur
3. Continuous murmur

Systolic Murmur: Systolic murmur is the murmur that is produced during systole. It is produced in the following conditions.

1. Incompetence of Atrioventricular Valves

• When the atrioventricular valves become weak, these valves cannot close completely.
• It causes the regurgitation of blood from the ventricles to the atria during ventricular systole producing the murmur. It is a harsh blowing sound with high frequency.

2. Stenosis of Semilunar Valves

• During stenosis of the aortic valve, the left ventricular pressure raises up to 300 mm Hg during systole.
• It causes greater turbulence in the blood flow. The vibrations of this sound can be felt as ‘thrills’ by palpation over the lower neck region and upper chest.
• In severe conditions, the sound is heard even a few feet away from the affected person. It is a harsh and loud sound.

3. Murmur due to Anemia: A systolic murmur is heard in severe anemia because of reduced viscosity and accelerated flow of blood.

4. Septal Defect: During interventricular septal defect, blood flows from the left ventricle to the right ventricle during systole It produces to systolic murmur. A septal defect is a rare disorder.

5. Coarctation of Aorta: Coarctation of the aorta is a congenital disorder characterized by the narrowing of a part of the systemic aorta. A loud murmur is produced during systole and it is heard in the earlier part of diastole also.

1. Stenosis of Atrioventricular Valves

• When the atrioventricular valves become narrow, the turbulence of blood flow occurs during diastole, i.e. when the blood enters the ventricles from the atria.
• Murmur due to stenosis of the mitral valve is heard better in the mitral area. The murmur due to the stenosis of the tricuspid valve is heard best in the tricuspid area.
• It is a weak sound with low frequency.
• Sometimes, the murmur due to mitral stenosis cannot be heard by stethoscope due to low frequency.
• But it can be felt as a mild thrill over a mitral area of the chest.

2. Incompetence of Semilunar Valves

• It is produced during the regurgitation of blood from the aorta into the ventricle through the incompetent semilunar valve during diastole.
• It is like a blowing sound with low frequency.

Continuous Murmur: H is Ihe murmur that is heard in conditions such as patent ductus arteriosus.

Patent Ductus Arteriosus

• The Intact ductus arteriosus is called patent ductus isdariosus .
• A continuous murmur is heard in ‘ihs condition. However, the intensity of the sound is more during systole and less during diastole.
• Because of this, it is also called a machinery murmur.
• It is a harsh blowing sound and is heard best in the pulmonary area. The murmur is heard one year after birth.